Purification and characterization of the cuticle-degrading proteases produced by an isolate of Beauveria bassiana using the cuticle of the predatory bug, Andrallus spinidens Fabricius (Hemiptera: Pentatomidae)

The entomopathogenic fungi-like
Beauveria bassiana
must penetrate via the integument of an insect to reach the hemocoel.
Since proteins are the molecules responsible for integument strength in insects, the proteins must synthesise the cuticle degrading
proteases which will then enable the proteases to penetrate. It is important to determine the biochemical properties of these proteases
so that fungal virulence can be better understood. In the current study, a recently collected isolate of
B. bassiana, namely AM-118, was
inoculated in liquid media containing 0.5% of
Andrallus spinidens
Fabricus
cuticle
to obtain specific proteases. The crude samples were
purified via a three step process using ammonium sulfate, Sepharyl G-100, and DEAE-Cellulose Fast Flow. The results revealed two
proteases known as subtilisin-like (Pr1), and trypsin-like (Pr2), with the molecular weights of 105 and 103 kDa. The optimal pH and
temperature values were found to be 8 and 35°C for Pr1 and 8 and 40°C for Pr2, respectively. Inhibitors like AEBSF, EDTA, TPCK, and
phenanthroline significantly affected proteolytic activities. Here, we reported two fungal proteases by high molecular weight from an
Iranian isolate of
B. bassiana. These findings will help us to better understand fungal virulence against insects.